From a sustainability perspective, electric vehicles are a big improvement over their traditional alternatives, to be sure. But all of these new vehicles "plugging in" will create a huge demand for energy from the grid. According to PG&E, one EV can draw as much power as three homes in San Francisco. Compounding this supply problem is the challenge of supplying this energy from clean, renewable sources, and determining whether new technologies to move energy around more efficiently — such as through a "smart grid" — could satisfy new demand without the need to build new generation.

One partial solution is shifting demand off-peak. Currently, PG&E offers special pricing for EV owners who charge their vehicles during off-peak hours in order to mitigate the demand on the grid. However, this may not be enough if EVs become as popular as Johns predicts.

In order to better understand the infrastructure needs of the future, PG&E and the Electric Power Research Institute recently began a pilot project to examine how different vehicles impact the electric grid throughout the day. Various groups around the Bay Area are helping cities figure out how to finance and build the necessary infrastructure to prepare for EVs to go commercial this fall, with the release of the Chevy Volt and Nissan Leaf.

Want to travel sustainably while EVs get figured out? SPUR recommends taking advantage of the old-fashioned clean transportation choices we have in the city: walking, biking and riding public transit.